Agrivoltaic Research, Applications Could Reconcile Trade-Offs at the Water-Food-Energy Nexus

A growing body of scientific research and real-world applications at the water-food-energy nexus is revealing that solar panels and photovoltaic (PV) energy systems on farm and ranch lands can not only produce emissions- and pollution-free energy but create a symbiosis that conserves water and results in higher agricultural productivity and biodiversity.

Cultivating plants under and around the PV panels creates a microclimate and habitats that are conducive to plant growth, water conservation and native biodiversity, as well as higher solar energy conversion efficiency, according to the research report, Solar PV Power Potential is Greatest Over Croplands. Exploring what have become known as agrivoltaic energy systems across a spectrum of types of land and variables key to solar power and agricultural production (solar insolation, air temperature, relative humidity, wind speed and direction and soil moisture), the OSU research team found that farmlands had the greatest median solar power potential per unit area of 17 scientific land use classifications, approximately 28 Watts per square meter (W/m2).

The research results could serve to reconcile conflicts of interest at the water-food-energy nexus regarding the trade-off between using land for agriculture or energy production.

The potential for dual-use, agrivoltaic systems may alleviate land competition or other spatial constraints for solar power development, creating a significant opportunity for future energy sustainability.

Ranking solar power potential across land use types

“[That] less than 1% of solar on agricultural lands is enough to offset global energy use tells me two things,” Chad Higgins, an associate professor in OSU’s College of Agricultural Sciences and corresponding author on the study, told Solar Magazine. “One that we should be doing this, and two, it’s not a lot of land percentage wise. We can focus on installing solar energy systems in locations where agrivoltaics make the most sense.” Contrary to conventional wisdom, solar PV installations in desert and arid areas ranked low, fifth, in the rankings.

The OSU agrivoltaics research group’s latest research results reveal the other side of the coin in terms of perspective as compared to the research group’s previous effort, Higgins explained in an interview.

With our first study, we really focused on how the presence of solar harvesting systems influence agricultural land use, hydrology and the broader ecosystem. This study comes from the opposite perspective: how does the ecosystem and its function influence the efficiency of solar panels, and what does that mean for farmers and in terms of land use?

Consisting of conventional, crystalline silicon, the solar PV panels tested during the initial stages of the research project were installed on OSU’s campus in Corvallis, Oregon some five or six years ago. Tesla, which monitors and manages the solar power system, shared the power production data it has been gathering with the research team so that they could carry out the project.

The first round of research results “made a lot thermodynamic sense for us, so we went ahead and derived an equation that made use of the first law of thermodynamics to predict solar panel efficiency given a set of environmental conditions,” Higgins explained.

The research team then used satellite data and images to create global maps and organize land-use types according to 17 scientific classifications. Then they ran simulated data through the model and compared the results with those obtained by running the actual microclimate data through the model. That confirmed its validity, which then allowed the researchers to expand its scope worldwide.

Laying down the cornerstones for agrivoltaic research and development

By creating and overlaying global maps of the results, the researchers were able to compare and rank solar power and agricultural productivity according to land-use types. Surprisingly, solar power productivity was highest on agricultural lands. Grasslands ranked second, while deserts and other relatively barren lands where there’s not a lot by way of vegetation ranked fifth. That runs contrary to the common industry siting practice of installing utility-scale solar power systems in deserts and flat, open drylands, at least in terms of solar power productivity, Higgins pointed out.

Besides being more productive in areas where solar insolation was high, “what our data showed was that the obvious was true: cooler air temperatures result in more productive solar panels,” Higgins said. Furthermore, “going from no to light winds increased productivity and panels were more productive in less humid conditions. Of course there are physical limits associated with solar panel power production and that changes with each new generation.”

Higgins and the OSU research team intend to continue “laying down the cornerstones” for applied agrivoltaics research and development that stakeholders of all stripes can point to and apply worldwide. “Agrivoltaics is an important piece of the sustainable farm of the future,” Higgins said.

Photo: Elnaz Hassanpour, Oregon State University

Higgins and team are doing just that in an effort to create a demonstration sustainable farm of the future. By doing so, they intend to illustrate “how we can change ‘non-sustainable’ farming practices to sustainable farming practices that increase farmers’ bottom lines, ensure that we can feed as many as 10 billion people, have enough energy to do so and avoid water-land-energy conflicts,” Higgins said. “All of these are constraints on farming practices and thus constraints on our food system. We’re trying to demonstrate how we can use technological innovation and advance work within sustainability constraints that feeds everyone and yields profits for agricultural industry and market players.”

Resolving challenges at the water-food-energy nexus

India is addressing challenges at the water-food-energy nexus by promoting and fostering growth of solar energy use on agricultural lands. Energy Efficiency Services Ltd. (EESL), a joint venture of public service enterprises (PSUs) working under the Ministry of Power in late August issued a tender to acquire 175,000 off-grid solar pumps on behalf of what are known as state nodal agencies, or SNAs. The tender specifies that water pumps with solar PV modules and pumps must be manufactured in India. In addition, the equipment must be approved as per Bureau of Indian Standards and MNRE guidelines.

A month earlier, India’s Ministry of New and Renewable Energy (MNRE) issued guidelines for the Pradhan Mantri Kisan Urja Suraksha evam Utthaan Mahabhiyan (PM-KUSUM) program, the primary goal of which is to raise India’s solar power capacity to 25.75 gigawatts (GW) by 2022. A major part of that is distributing standalone and grid-connected solar pumps to farmers across the country.

A growing number of farmers, ranchers and government leaders in the US are recognizing the benefits agrivoltaics can convey, as well. They’re agreeing to lease some of their farmlands to solar power project developers. State government leaders are introducing new, or modifying existing, policies, legislation and regulations, to take advantage of and capitalize on the benefits agrivoltaics can provide.

A recent change in government leadership and the enactment of pro-solar policies and goals in the northeastern state of Maine provides a case in point. “Right now Maine is at a turning point. We had just changes in solar policy at the state house that are greatly going to incentivize the development of solar power,” Andy Smith, co-owner of a dairy products business was quoted in a local news report. “And overnight farmers like myself are being contacted by out-of-state investment companies looking to lease land for 20–25 years.”

Similar developments are taking place in Pennsylvania, where state Farm Bureau Spokesman Mark O’Neill told news media that there has been a surge of interest on the part of solar energy companies to lease farmland and build solar PV systems across the Mid-Atlantic state. London, UK-based solar power project developer Lightsource BP recently signed long-term contracts to lease 500 acres (202 hectares) of farmland from seven Franklin County farmers in order to build a 70-MW solar farm in a deal that’s said will be the largest solar power installation in the state.

Penn State University will purchase the emissions-free electricity, which is projected to meet one-quarter of electricity demand across the state university’s campuses once it’s completed in July 2020. The farmers will be collecting lease payments for 30 years, according to a local news report.

“Over the next couple of years, the Lightsource BP project will probably be on the smaller end,” said Carl Jackson, director of utility-scale solar projects at Penn State. “Pennsylvania has a tremendous amount of farmland, the cost [of solar] has come down, and the state has taken some initiatives to promote solar.”

US solar project developers and farmers in Minnesota are at the leading edge of change. They’re not only looking to install solar PV systems to meet their own energy needs, better manage water and agricultural resources and add new streams of revenue that can make up for lost revenues due to international trade tariffs and all the other risks associated with raising crops and livestock for a living. They’re looking to find ways of siting and designing solar PV systems so as to create a symbiosis between water and energy use and farming methods and practices that yield net benefits across the board.

Creating symbiosis at the water-food-energy nexus

An agricultural solar-plus-storage demonstration project being carried out by Connexus Energy in Minnesota aims to deliver more than emissions-free electricity, for example. Native prairie grasses and flowers are being planted under and around the solar PV panels it’s building on farmland on which pumpkins and melons are grown.

“Pollinator-friendly plantings at large solar energy sites have become common in Minnesota in recent years. Not only do they provide habitat for the bee and butterfly populations people have been concerned about, but they also promote soil health and probably even boost the solar panels’ electricity output on warm days,” according to a local news report.

Professional investment groups are showing growing interest in agrivoltaics and investing in companies and ventures that aim to meet challenges at the water-food-energy nexus.

Sheep graze between rows of solar panels | Photo: NC State University

In the wake of a successful pilot program in Jacksonville, Florida, renewable energy-energy storage investment group C2C Capital announced it was scaling up its 7-MW solar-plus-storage sheep vegetation maintenance program. The company expects to pare down its vegetation maintenance costs across all the 10 solar projects in its portfolio, a total of 79 MW, as well as reduce its carbon emissions footprint and open up new business development opportunities for farmers across the southeast US.

C2 Energy Capital is also carrying out a site-vegetation management test program by planting wildflowers so as to reduce the need for mowing and to create habitat for pollinators, more particularly for bees.“In the next phase, we’ll scale up our solar sheep program to projects covering over 300 acres in three states and drive down ground maintenance costs. It’s a win-win situation that makes good business sense for everyone involved,” C2C Energy Capital Director of Asset Management, was quoted in a press release.

Downstream agrivoltaic energy, food storage, processing and logistics

The potential for conflicts regarding water and land use increase in parallel with scarcity of these natural resources. Not only are digital solar energy and solar-plus-storage systems playing a central role on farms and ranches, they’re playing central roles in downstream sustainable agriculture initiatives around the world. In addition to solar water pumps for irrigation, social enterprises and impact investors are teaming up with smallholders and larger farm owners in emerging and lesser-developed countries to reduce food waste and loss, for instance.

The United Nations’ Food and Agriculture Organization (FAO) estimates that roughly one-third of the food produced for human consumption—a US$5 trillion market—each year is lost or wasted—an estimated 1.3 billion metric tons. In addition to food loss and waste, the agriculture sector is a huge consumer of water, a major source of pollution and the world’s largest human sources of carbon and non-carbon greenhouse gas emissions.

Developers of the Ecofrost solar-powered cold storage room, the founders of India’s Ecozen Solutions are working with farmers to install the technology to improve post-harvest management along the “first mile” of the food supply chain. With Ecofrost, farmers can keep as much as five metric tons of crops chilled for as long as 30 hours, a dramatic improvement that has enabled farmers to reduce food waste and loss by 20% and boosted their incomes by 50% and even as much as 100%, according to a news report. To date, 150 units have been installed across India, according to the company’s chief operating officer.

Creating the sustainable farm of the future

All that said, those fostering widespread use of agrivoltaics faces substantial hurdles. Threatened by recurring droughts, farmers in Zimbabwe are realizing the benefits of a solar-plus-storage irrigation system that has improved crop yields and incomes substantially. The microgrid has created another problem, a potentially fatal one at that, however. The water and green fields of crops are attracting herds of wild elephants, who typically sneak their way in at night to avoid the night patrols farmers have organized to scare them away.

More broadly speaking, the agricultural sector in countries around the world is fragmented, particularly so in those where smallholder farms are the norm. That makes it difficult to recruit participants and organize a market for agrivoltaics sizable and persistent enough to attract the interest, and capital, of banks, investment groups and large solar energy industry players.

Ecozen leases its Ecofrost cold rooms in order to bring down upfront costs and make them affordable for farmers, particularly those who harvest just three to six months of the year. The payback period is three to four years and varies by commodity and business model, management explained.

Incorporating the latest digital information and communications technologies, including machine learning and artificial intelligence, conveys other substantial improvements. For farmers, data can mean “growing the right produce at the right time in a way that’s climate-friendly, and for which there’s demand in the market.”

In addition, it enables parties all along the supply chain to trace commodities from the farm through wholesale markets and intermediaries and onward to retail outlets, for example. Market participants and regulators are then able to aggregate that data and share it so that warehousing companies, exporters, food processors and bankers have access to credible information about farmers and the volume and quality of their produce, Ecozen highlights.

More broadly speaking, overcoming traditional, conventional attitudes regarding agriculture, energy and water use may be the biggest and most fundamental hurdle, Higgins pointed out. “It’s early days here in Oregon…We’re working with companies and individual donors to create a commercial production-scale demonstration sustainable farm of the future,” he said.

Higgins said the OSU research team is close to raising the funding needed to acquire and install a suitable agrivoltaic energy system for their demonstration sustainable farm of the future.

If we can get that, the opportunities could start multiplying and we’d be able to really get something rolling. You have to understand that this type of system doesn’t exist in the real world yet. It’s not part of how we think about agriculture, so we need to get past that gap in perception.

“A solar panel installation doesn’t have to look like it does today, and it can be incorporated with sustainable agriculture practices. We can engineer our way out of perceived conflicts [at the water-food-energy nexus],” Higgins concluded. “But that’s going to take a paradigm shift in terms of our views of the agricultural system…a conscious effort to put agriculture first, and make sure agricultural needs are met. Then we can chase down sustainable energy solutions.” comment

Solar Magazine is an online solar PV magazine comprised of various aspects of the solar energy industry. We share news, technologies, developments and insights. We’re integrating forces to help better promote the development of the industry. And we seek the universalization of solar lifestyle.